1. Field of the Invention
The prevent invention relates to a paper feeding apparatus used as a paper feeding mechanism of a printing apparatus or an image forming apparatus, further in details, relates to a paper feeding apparatus for feeding sheet mounted on a sheet base to a printing region or the like of a printing apparatus by rotating a paper feeding roller.
2. Description of the Related Art
FIG. 4 is an outline vertical sectional view showing an essential portion of a paper feeding apparatus according to a prior art example. The paper feeding apparatus includes a sheet base 1 mounted with sheet S, a base portion 2 for supporting a sheet end S1 of the sheet 1 mounted on the sheet base 1, and a paper feeding roller unit 3. The sheet base 1 is divided into a fixed inclined portion 11 and a movable portion 12, and whereas the fixed inclined portion 11 is inclinedly raised from the base portion 2, the movable portion 12 is erectable and fallable centering on a lateral shaft 13 arranged at a constant position by being supported by a side plate portion 21 arranged at a side portion of the base portion 2. Further, when the movable portion 12 is brought into a fallen attitude as shown by a bold line of the drawing by being folded as shown by an arrow mark a, the movable portion 12 covers the paper feeding roller unit 3 from above and when the movable portion 12 is brought into an erected attitude as shown by an imaginary line of the drawing by being developed as shown by an arrow mark b, the movable portion 12 is extended to an upper side of the fixed inclined portion 11 to support a portion of the sheet S mounted on the fixed inclined portion 11 projected from the fixed inclined portion 11. Further, the paper feeding roller unit 3 include a paper feeding roller 32 and a rotation transmitting mechanism 33 cooperatively connected with the paper feeding roller 32 in a case 31 having a prolonged vertical length and the rotation transmitting mechanism 33 is formed by a gear train having an input ring member 34 including a gear arranged upward from the paper feeding roller 32. Further, a shaft member 35 as a rotating shaft of the input ring member 34 is supported by the side plate portion 21 to project to an outer side therefrom and the outer side of the side plate portion 21 is attached with a driven gear 36 rotated by being brought in mesh with a drive gear (not illustrated) rotated by being transmitted with rotation of a motor.
According to the paper feeding apparatus having the constitution, the sheet end S of the sheet S mounted on the fixed inclined portion 11 is supported by the base portion 2. Further, when the paper feeding roller 32 of the paper feeding roller unit 3 is brought into contact with the sheet S to rotate, the sheet S is fed to slide on the base portion 2 by the rotation. In the paper feeding apparatus, a position at which the paper feeding roller 32 is brought into contact with the sheet S in feeding paper, that is, a position of operating the paper feeding roller 32 is determined to a predetermined position upward from the base portion 2 and a friction face 14 is formed on a side of the fixed inclined portion 11 in correspondence with the position. The friction face 14 serves to prevent overlappingly feed sheet such that when the sheet S is laminated on the fixed inclined portion 11, lowermost side sheet follows the sheet S fed by the paper feeding roller 32 to feed.
As described above, according to the paper feeding apparatus of the prior art, the position of operating the paper feeding roller 32 is determined at the predetermined position upward from the base portion 2, further, a height of installing the paper feeding roller unit 3 having the paper feeding roller 32 is determined to be constant by a height of installing the shaft member 35 supported by the side plate portion 21. Therefore, a position of a height of the movable portion 12 in constituting the fallen attitude of folding the movable portion 12 and covering the paper feeding roller unit 3 is restricted by the height of installing the paper feeding roller unit 3.
There is known other prior art example in which in a paper feeding apparatus of an image forming apparatus, a sheet laminating plate (in correspondence with the above-described movable sheet base) is attached with a sheet end supporting portion (in correspondence with the above-described base portion) for supporting a sheet end of sheet and a paper feeding roller (in correspondence with the above-described sheet feeding roller) to thereby unitize the sheet laminating plate, the sheet end supporting portion and the paper feeding roller (refer to, for example, JP-A-8-239126). According to the paper feeding apparatus, the sheet laminating plate is made to be erectable and fallable centering on a rotational axis line of a feed roller for carrying sheet to a printing portion, when the sheet laminating plate is erected to contain at a back portion of an apparatus main body, the paper feeding roller is also contained in the apparatus main body and when the sheet laminating plate is fallen to a back side of the apparatus main body to project to the back portion, also the paper feeding roller is projected to a side portion of the apparatus main body to thereby enable to feed sheet mounted on the sheet laminating plate. By adopting the constitution, the image forming apparatus can be downsized, particularly, a size of the apparatus main body in a front and rear direction can be shortened.
According to the paper feeding apparatus of the prior art explained in reference to FIG. 4, the position of operating the paper feeding roller 32 is determined to the predetermined position upward from the base portion 2, the height of installing the paper feeding roller unit 3 is determined to be constant and therefore, as described above, the position of the height of the movable portion 12 in constituting the fallen attitude of folding the movable portion 12 of the sheet base land covering the paper feeding roller unit 3 is restricted by the height of installing the roller unit 3. Therefore, there poses a problem that it is restricted by a structure of attaching the paper feeding roller unit 3 to downsize the apparatus by restraining a total height H2 of the paper feeding apparatus in bringing the movable portion 12 into the fallen attitude to be low.
Meanwhile, according to the prior art example described in JP-A-8-239126, the paper feeding roller for feeding sheet mounted to the sheet laminating plate is unitized integrally with the sheet laminating plate and therefore, the position of the sheet laminating plate in erecting the sheet laminating plate to contain to the apparatus main body is not restricted by the paper feeding roller and the apparatus can be downsized by restraining the size of the apparatus main body in the front and rear direction to be short. However, according to the paper feeding apparatus described in JP-A-8-239126, also the sheet end supporting portion for supporting the sheet end of sheet mounted on the sheet laminating plate is integrated to the sheet laminating plate along with the paper feeding roller and therefore, when the sheet laminating plate is erected or fallen, also a member for supporting the sheet end of sheet is erected or fallen along with the paper feeding roller and a positional relationship among three members of the sheet laminating plate, the paper feeding roller and the sheet end is always maintained constant.
In contrast thereto, according to the prior art example explained in reference to FIG. 4, the sheet base 1 is divided into the fixed inclined portion 11 and the movable portion 12, the fixed inclined portion 11 is raised integrally from the base portion 2 and therefore, the sheet base 1, the base portion 2 and the paper feeding roller unit 3 cannot be integrated by applying the technology described in JP-A-8-239126.